#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int a = -1;
	double sum = 0;
	double term = 0;
	for (int i = 1; i <= 100; i++)
	{
		a = a * (-1);
		 term = (double)1 / i;
		sum = sum + term * a;
	}
	printf("%lf",sum);
	return 0;
}